1. Field of the Invention
The invention relates to a micropump comprising a pump membrane which can be moved by modifying the volume of the pump chamber which is adjacent to the pump membrane and a base part, also comprising two valves which area arranged in recesses in the base part and react to the pressure in the pump chamber in order to alternately open and close an inlet channel and an outlet channel for a medium to be pumped.
The invention further relates to a method for producing such a micropump.
2. Description of the Related Art
The lateral measurements of such micropumps which are fully or predominantly made of plastics are preferably between 5 and 30 mm for a height of 0.5 to 5 mm. The pump rates for fluids range between 10−5 and 0.2 l/min. The main fields of application include chemical and biochemical analytics, microreaction technology, the conveyance of gases, the conveyance and dosage of pharmaceutical agents, specimen fluids, adhesives, fuels or lubricants.
Plastic micropumps have the advantage over pumps made of silicon or metals that apart from the utilization of inexpensive base materials, efficient production methods such as injection molding can be deployed. Depending on the requirements for example in connection with optical transparency, stability, hydrophilicity, hydrophobicity or chemical resistance, different plastics may be deployed using the same construction, such as for example polycarbonate, polypropylene, polyethylene, cyclo-olefin-copolymer, polyetheretherketone, polyphenylensulfide or fluorine plastics.
DE 44 02 119 describes a micropump made of plastic comprising a membrane arranged between two shell halves which serves as a pump membrane as well as for forming movable valve bodies, and which is open-worked at valve seats.
A micropump of the afore-mentioned type is known from DE 197 20 482. By forming a pump chamber, a pump membrane is mounted on the top side of a two-part base part having recesses for valves in its interior, which can be deformed by means of a piezo actuator. A valve membrane arranged between both parts of the base part has a gap on both valve seats and thus comprises a component common to both valves.
By using relatively large valve membranes which are involved in forming both valves, the production of such micropumps is very costly. It is particularly problematic to arrange the gaps in the membrane on the valve seats with the accuracy necessary for the functioning of the valves. On the one hand, the distortion and shrinkage effects typical for plastic materials lead to big position fluctuations of the gaps on the membrane. On the other hand, misplacements of the gaps on the valve seats can occur rather easily during the assembly of the thin and cumbersome membrane film. The production yield under the conditions of serial production is thus very low.